The present invention relates to controlling a speed of a head which is used for magnetic disc drives and other disc drives. More particularly it relates to a method of driving head, a head driving device and a disc driving apparatus using the same method and device. When an access to a designated sector is required, the present invention allows the method of driving the head, the head driving device and the disc driving apparatus using the same method to reduce power consumption at seek-operation free from extending an access time to the designated sector.
When a demand for reading/writing any sector on a disc occurs, a conventional magnetic-disc-driving apparatus moves a magnetic head from a present position to a track including a target sector, within a shortest time, and when the disc rotates thereby the target sector arrives at a position accessible by the magnetic head, the magnetic head reads/writes data in the target sector. (Hereinafter the track including a target sector, or the track a target sector is in is refereed to simply as TTS.) Therefore, in any cases for reading/writing, the conventional magnetic-disc-driving apparatus has required a waiting time from an instant when the magnetic head finishes a seek-operation to TTS, to another instant when the disc rotates thereby the target sector arrives at the position the magnetic head can read/write data.
In order to reduce such a waiting time, the following methods have been employed. When the magnetic-disc-driving-apparatus reads/writes across two tracks or more in series, for example, when the disc-driving-apparatus finished reading/writing a first track and then reads/writes a second track continuously, the apparatus places the leading sector of the second track at a position so that a seek-time for the head from the first track to the second track can be minimized. This mechanics reduces the waiting times required at each access sequentially to sectors across the tracks. However, this mechanics cannot reduce the waiting times at random accesses.
When the magnetic-disc-driving-apparatus reads/writes any sector on the disc, a circuit of read/write dataxe2x80x94necessary for reading/writing a sectorxe2x80x94must be activated. In order to save the power, a method is available for activating the circuit only when the sector is engaged in read/write. The disc driving apparatus using this method turns on the circuit of read/write data at a predetermined timing such as before, after, during the seek, or just before reading/writing the sector, and the disc driving apparatus turns off the circuit at a timing the magnetic disc finishes reading/writing. As a result, the power consumption is reduced.
Although the conventional magnetic-disc-driving-apparatus cannot access to a target sector until the head arrives at a position accessible to a target sector, the driving apparatus moves the head to TTS in a minimum time responding to each media-access-demand. The disc driving apparatus requires large force to move a head assembly to TTS at a maximum speed. In other words, the disc driving apparatus feeds large current to a head assembly-drive-circuit every time the head moves. Therefore the power consumption during the seek-operation becomes greater, and this inversely affects the efforts of lowering the power consumption.
The circuit of read/write data requires a time until the circuit of read/write data gets to work normally. Therefore, in a case of employing a control method that turns on the circuit of read/write data at a predetermined timing, without considering the times such as the seek-time the head moves to TTS, the time until the head arrives at a position accessible to the target sector after a seek-operation, or the time until the circuit of read/write data gets to work normally and so on, the following inconveniences may occur: Depending on a target sector position after finishing the seek-operation and a startup timing for the circuit of read/write data, although the head already arrived at the position accessible to the target sector, the disc must wait to rotate because the circuit of read/write data is not ready for an operation. The circuit of read/write data is thus obliged to stay activated unnecessarily long. These factors impede lowering the power consumption.
A method for driving a head of the present invention resolves the problems mentioned above, and the method comprises the following steps:
(a) a step for determining a head position by head-position-data supplied from a head-position-detector;
(b) a step for calculating in advance a time the head can access to a target sector of a disc for the first time, based on the data of the head-present-position, location data of the target sector at a destination, and driving capability of the head assembly; and
(c) a step for controlling a head-assembly-driver by determining a moving-speed and acceleration/deceleration pattern for the head so as to finish the seek-operation to TTS (the track including a target sector) during the time mentioned in (b).
More specifically, the method comprises the steps as follows:
(a) a step for determining a minimum integer N of integers each of which holds a relation:
(a target-sector-accessible-time )xe2x89xa7(a shortest time for the head to move to TTS),
Assume that a sector-arrival-time is a necessary time from an instant the head starts moving to TTS to another instant the disc rotates thereby the target sector arrives at a position the head can access to for the first time, and
the target-sector-accessible-time is a sum of the sector-arrival-time and a rotation-waiting-time (latency), where the latency is obtained by multiplying a disc-rotation-period by an integer N (zero or greater than zero);
(b) a step for moving the head by determining the moving-speed and acceleration/deceleration pattern of the head so as to finish a head-moving and a head-positioning to TTS within the target-sector-accessible-time determined by substituting the integer N into a formula:
(the sector-arrival-time+the disc-rotation-periodxc3x97the integer N)
In comparison with conventional methods, the method of the present invention can provide a method realizing a reduction of power consumption during a seek time without extending an access time.
A head driving device of the present invention comprises the following elements:
(a) a head accessing to a disc;
(b) head-position detecting means for finding a head-present-position
(c) target-sector-accessible-time calculation means for calculating a target-sector-accessible-time, in advance, the head can access to a target sector for the first time, based on head-present-position data, location data of the target sector at a destination, and driving capability of the head assembly; and
(d) control means for controlling a head-assembly-driver by determining a moving-speed and acceleration/deceleration pattern for the head so as to finish a seek-operation to TTS during the time described in (c).
More specifically, the head driving device comprises the following elements:
(a) a head accessing to a disc;
(b) target-sector-accessible-time calculating means for determining a minimum integer N that holds a relation:
(the target-sector-accessible-time)xe2x89xa7(a shortest time the head moves to TTS),
where a sector-arrival-time is defined as a necessary time from a instant the head starts moving to TTS to another instant the disc rotates thereby the target sector arrives at a position the head can access to for the first time, and
the target-sector-accessible-time is a sum of the sector-arrival-time and a latency, where the latency is obtained by multiplying a disc-rotation-period by an integer N (zero or greater than zero);
(c) control means for moving the head by determining the moving-speed and acceleration/deceleration pattern of the head so as to finish a head-moving and a head-positioning to TTS within the target-sector-accessible-time determined by substituting the integer N into a formula:
(the sector-arrival-time+the disc-rotation-periodxc3x97the integer N)
In comparison with conventional devices, the present invention provides a head driving device realizing a reduction of power consumption during a seek time without extending an access time.
A disc driving apparatus of the present invention comprises the following elements:
(a) a spindle unit for rotating a disc; and
(b) a head driving device, the device including the structure discussed above.
In comparison with conventional apparatuses, the present invention provides a disc driving apparatus realizing a reduction of power consumption during a seek time without extending an access time.